During every cell division, the genome must accurately replicate and segregate a complete set of chromosomes into each daughter cell. Failures in chromosome segregation and gene regulation have severe consequences for human health, since creating cells with an inappropriate chromosome number can lead to aneuploidy and chromosome instability. Chromosome structure also plays a key role in promoting accurate gene expression to avoid cancer progression. Therefore, it is of prime importance to understand the various mechanisms regulating chromosome structure, and the long-term goal of my research is to define the molecular machinery and mechanisms that govern chromosome structure to ensure genomic stability. Conserved multiprotein complexes known as condensins are key regulators of chromosome architecture, and increasing evidence suggests that condensins play broader roles than previously appreciated, including gene silencing. In preliminary results, it was unexpectedly discovered that condensin II physically interacts with proteins that are associated with chromatin-based silencing and required for transgene silencing phenomena. Thus, this proposal aims to test the hypothesis that the mitotic condensin II complex in Caenorhabditis elegans (C. elegans) cooperates with the RNA interference (RNAi) machinery and chromatin proteins to establish heterochromatin and mediate gene expression. Using biochemical and genetic approaches: (1) The apparent interactions between condensin II and RNAi and chromatin proteins will be confirmed. Moreover, condensin-interacting proteins will be tested to determine if they contribute to chromosome segregation and are required for condensin recruitment. (2) Transgene assays will be utilized to investigate whether condensin II is required for related forms of chromatin-based silencing. (3) It will determined if small RNAs associate with condensin II and are required for its functions in chromosome assembly. These studies will provide insights into how these conserved mechanisms ensure the accurate building, expression, and segregation of chromosomes and avoid the chromosomal abnormalities often observed in cancers.